This invention relates generally to nozzles for use with fire fighting equipment, and more particularly to a multifunction nozzle which has straight stream, fog and foam modes of operation.
The traditional method of extinguishing a fire has been to spray water on a burning object in order to wet it sufficiently to stop the burning. However, this method is not effective when the source of the fire is a flammable liquid-vapor such as gasoline or benzene; foam generators and nozzles have been developed which are very effective with such fires. Special-purpose nozzles have been developed to spray a layer of foam over the liquid, which prevents the flammable vapor from forming.
Very recently foam has also been used against fires in forests and wildlands, and it has been quite effective and desirable for a number of reasons. Water is usually in short supply in such areas, and foam can increase the effectiveness of a given quantity of water by a factor of 5 to 10 times because the total volume of foamed water is much greater than water alone because of the air in the foam bubbles. Some trees, such as pine and eucalyptus, are very oily, and whereas water tends to run off such trees, foam will stick to the trees and provide protection. Still further, the foam concentrate, or foam generating liquid, may include a water surface tension reducing agent which helps the foamed water to penetrate the combustible layer of material on the ground, or duff, and help to extinguish ground fires.
Prior art foam nozzles have been developed and used in forest fire situations but such nozzles have been special purpose or dedicated use nozzles. In other words, prior art foam nozzles cannot be also used as a fog nozzle or as a straight stream nozzle. Consequently it has been necessary to change nozzles when it is desired to switch from foam operation to straight stream or fog operation. When fighting a fire, especially in a forest, it is highly desirable to be able to switch, very quickly, from one mode of operation to another.
It is therefore a general object of the present invention to provide a multifunction nozzle which may be used in either foam, fog or straight stream modes of operation.